Flat panel display (“FPD”) devices may include liquid crystal display (“LCD”) devices and electroluminescence (“EL”) devices. An EL device is a device which makes use of the phenomenon of electroluminescence to emit light. An EL device generally includes thin film transistors (“TFT”) and an organic light-emitting diode (“OLED”) further including a light-emitting layer. When a current passes between a cathode and an anode of the OLED device, light is emitted through the light-emitting layer.
Conventional organic EL devices can be designed to include two panels for dual display or double display: a main panel and a sub-panel. Generally, the main panel serves to provide main display functions of an electronic product, and the sub-panel serves to provide subsidiary display functions such as a caller identity display or a clock display. The main panel and the sub-panel are generally independent of each other, and include individual substrates, resulting in a disadvantageous increase in device size.